2020-06-08 03:29:51 +03:00
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package gif
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// https://www.w3.org/Graphics/GIF/spec-gif87.txt
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// https://en.wikipedia.org/wiki/GIF
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// https://web.archive.org/web/20160304075538/http://qalle.net/gif89a.php#graphiccontrolextension
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// TODO: local color map
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// TODO: bit depth done correct?
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import (
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"bytes"
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2021-08-17 13:06:32 +03:00
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"github.com/wader/fq/format"
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"github.com/wader/fq/pkg/decode"
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2022-07-16 19:39:57 +03:00
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"github.com/wader/fq/pkg/interp"
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2021-12-02 00:48:25 +03:00
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"github.com/wader/fq/pkg/scalar"
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2020-06-08 03:29:51 +03:00
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)
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func init() {
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2022-07-16 19:39:57 +03:00
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interp.RegisterFormat(decode.Format{
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2020-06-08 03:29:51 +03:00
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Name: format.GIF,
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Description: "Graphics Interchange Format",
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Groups: []string{format.PROBE, format.IMAGE},
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DecodeFn: gifDecode,
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})
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}
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const (
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extensionPlainText = 0x01
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extensionGraphicalControl = 0xf9
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extensionComment = 0xfe
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extensionApplication = 0xff
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)
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2022-09-30 14:58:23 +03:00
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var extensionNames = scalar.UintMapSymStr{
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2020-06-08 03:29:51 +03:00
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extensionPlainText: "PlainText",
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extensionGraphicalControl: "GraphicalControl",
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extensionComment: "Comment",
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extensionApplication: "Application",
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}
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func fieldColorMap(d *decode.D, name string, bitDepth int) {
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2021-11-05 17:04:26 +03:00
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d.FieldArray(name, func(d *decode.D) {
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2020-06-08 03:29:51 +03:00
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for i := 0; i < 1<<bitDepth; i++ {
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d.FieldArray("color", func(d *decode.D) {
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d.FieldU8("r")
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d.FieldU8("g")
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d.FieldU8("b")
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})
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}
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})
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}
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2023-02-18 23:10:48 +03:00
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func gifDecode(d *decode.D) any {
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d.Endian = decode.LittleEndian
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2022-09-30 14:58:23 +03:00
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d.FieldUTF8("header", 6, d.StrAssert("GIF87a", "GIF89a"))
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2021-10-19 02:53:37 +03:00
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2020-06-08 03:29:51 +03:00
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d.FieldU16("width")
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d.FieldU16("height")
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gcpFollows := d.FieldBool("gcp_follows")
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2022-09-30 14:58:23 +03:00
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d.FieldUintFn("color_resolution", func(d *decode.D) uint64 { return d.U3() + 1 })
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2020-06-08 03:29:51 +03:00
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d.FieldU1("zero")
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2022-09-30 14:58:23 +03:00
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bitDepth := d.FieldUintFn("bit_depth", func(d *decode.D) uint64 { return d.U3() + 1 })
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2020-06-08 03:29:51 +03:00
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d.FieldU8("black_color")
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d.FieldU8("pixel_aspect_ratio")
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if gcpFollows {
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fieldColorMap(d, "global_color_map", int(bitDepth))
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}
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2021-11-05 17:04:26 +03:00
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d.FieldArray("blocks", func(d *decode.D) {
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blocks:
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for {
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2023-03-10 03:14:53 +03:00
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switch d.PeekUintBits(8) {
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2022-01-24 23:21:48 +03:00
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case ';':
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2020-06-08 03:29:51 +03:00
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break blocks
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2022-01-24 23:21:48 +03:00
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case '!': /* "!" */
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2021-11-05 17:04:26 +03:00
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d.FieldStruct("extension_block", func(d *decode.D) {
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d.FieldU8("introducer")
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2022-09-30 14:58:23 +03:00
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functionCode := d.FieldU8("function_code", extensionNames, scalar.UintHex)
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2020-06-08 03:29:51 +03:00
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dataBytes := &bytes.Buffer{}
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2021-11-05 17:04:26 +03:00
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d.FieldArray("func_data_bytes", func(d *decode.D) {
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2020-06-08 03:29:51 +03:00
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seenTerminator := false
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for !seenTerminator {
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2021-11-05 17:04:26 +03:00
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d.FieldStruct("func_data_byte", func(d *decode.D) {
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byteCount := d.FieldU8("byte_count")
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b := d.FieldRawLen("data", int64(byteCount*8))
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if d.PeekUintBits(8) == 0 {
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2020-06-08 03:29:51 +03:00
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d.FieldU8("terminator")
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seenTerminator = true
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}
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2022-06-30 13:13:36 +03:00
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d.CopyBits(dataBytes, d.CloneReadSeeker(b))
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2020-06-08 03:29:51 +03:00
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})
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}
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})
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_ = functionCode
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// TODO: need a FieldStructBitBuf or something
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// switch functionCode {
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// case extensionGraphicalControl:
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2021-08-16 13:46:59 +03:00
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// d.FieldFormatBitBuf(
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2020-06-08 03:29:51 +03:00
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// "graphics_control",
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2022-01-24 23:21:48 +03:00
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// bitio.NewReader(dataBytes.Bytes(), -1),
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2020-06-08 03:29:51 +03:00
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// )
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// }
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})
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2022-01-24 23:21:48 +03:00
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case ',':
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d.FieldStruct("image", func(d *decode.D) {
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d.FieldU8("separator_character")
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d.FieldU16("left")
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d.FieldU16("top")
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d.FieldU16("width")
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d.FieldU16("height")
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localFollows := d.FieldBool("local_color_map_follows")
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d.FieldBool("image_interlaced")
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d.FieldU3("zero")
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2022-09-30 14:58:23 +03:00
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d.FieldUintFn("bit_depth", func(d *decode.D) uint64 { return d.U3() + 1 })
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2020-06-08 03:29:51 +03:00
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d.FieldU8("code_size")
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if localFollows {
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fieldColorMap(d, "local_color_map", int(bitDepth))
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}
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2021-11-05 17:04:26 +03:00
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d.FieldArray("image_bytes", func(d *decode.D) {
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2020-06-08 03:29:51 +03:00
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seenTerminator := false
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for !seenTerminator {
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2021-11-05 17:04:26 +03:00
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d.FieldStruct("func_data_byte", func(d *decode.D) {
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2020-06-08 03:29:51 +03:00
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byteCount := d.FieldU8("byte_count")
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2021-11-05 17:04:26 +03:00
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d.FieldRawLen("data", int64(byteCount*8))
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2023-03-10 03:14:53 +03:00
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if d.PeekUintBits(8) == 0 {
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2020-06-08 03:29:51 +03:00
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d.FieldU8("terminator")
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seenTerminator = true
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}
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})
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}
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})
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})
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2021-11-16 19:11:26 +03:00
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default:
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2021-11-17 18:26:13 +03:00
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d.Fatalf("unknown block")
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}
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}
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})
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d.FieldU8("terminator")
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return nil
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}
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